Monitoring platform for detection of hypovolemia, hemorrhage and blood loss

ABSTRACT

Systems and techniques are provided for monitoring hydration. In one implementation, a method includes measuring an electrical impedance of a region of a subject to generate an impedance measurement result. The result may be correlated with a blood loss condition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 60/606,778 filed Sep. 2, 2004 and entitled “NON-INVASIVE MONITORINGPLATFORM FOR DEHYDRATION, BLOOD LOSS, WOUND MONITORING, AND ULCERDETECTION,” the content of which is incorporated herein by reference.

BACKGROUND

Many species of organisms are largely water. The amount and/ordisposition of water in an individual organism (i.e., the hydration ofthe organism) has been correlated with the health of the individualorganism. For example, an excess or a scarcity of water can beindicative of acute and/or chronic disease states. Changes in bodycomposition such as percent fat content and the like can also result inchanges in body water content.

Because the electrical impedance of an organism will vary with changesin water content, impedance measuring devices have been devised that areintended to provide indications of total body water based on measuredbody impedance. Although such devices have been found useful in someapplications, the potential of bioimpedance data to supplement medicaldiagnosis and treatment has not been fully realized.

SUMMARY

In one embodiment, the invention comprises a method of detecting and/ormonitoring hypovolemia, hemorrhage or blood loss of a subject comprisingmaking impedance measurements of at least a portion of the subject whileor after the subject is injured.

In another embodiment, a method of monitoring a hydration-relatedcondition of an injured subject, e.g. hypovolemia, hemorrhage or bloodloss, comprises monitoring a bioelectric impedance of at least a regionof the injured subject; generating data related to the hydrationcondition of the subject; and communicating the hydration condition tomedical personnel attending the subject.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a probe for monitoring the hydration of an organism.

FIG. 2 shows a bioelectric impedance spectroscopy probe for monitoringthe hydration of an organism.

FIG. 3 shows a bandage bioelectric impedance spectroscopy probe.

FIGS. 4A and 4B illustrate example deployments of a bioelectricimpedance spectroscopy probe and a bandage probe to monitor hydration.

FIGS. 5 and 6 show a portable strap bioelectric impedance spectroscopyprobe.

FIGS. 7, 8A, 8B, 8C, 9A, and 9B illustrate example deployments of astrap probe to monitor hydration.

FIGS. 10A and 10B show other strap bioelectric impedance spectroscopyprobes.

FIG. 10C shows a graph of example hydration monitoring results that canbe obtained using a bioelectric impedance monitor and a skin temperaturethermometer.

FIG. 11 shows a system for monitoring the hydration of an organism.

FIG. 12 shows a data collection apparatus that is usable in a system formonitoring the hydration of an organism.

FIG. 13 shows another system for monitoring the hydration of anorganism.

FIG. 14 shows another system for monitoring the hydration of anorganism.

FIG. 15 illustrates an example deployment of multiple strap probes tomonitor hydration.

FIG. 16 shows another system for monitoring the hydration of anorganism.

FIG. 17 shows an example of a model equivalent circuit that can be usedin monitoring the hydration of an organism.

DETAILED DESCRIPTION

As mentioned above, impedance monitoring and measurements have beenunderutilized. In particular, the use of bioimpedance to assesshydration change associated with blood loss, either externally throughwounds or other mechanisms or internally resulting in sequestration ofbody fluids, including blood, in non-exchangeable pools of water withinthe body, has not been implemented. Set forth below are a variety ofsystems and methods that can be utilized to extend this technique tothese applications.

FIG. 1 shows a probe 100 for monitoring the hydration of an organism.Probe 100 includes a body 105, an energy source 110, and a sensingcircuit 115. Body 105 can be a flexible member in that it can becontoured to follow the skin surface or other portion of an organism,such as, for example, a patch or strap. Body 105 supports probe/organisminterfaces 120, 125, 130, 135 which apply or exchange energy with thesubject and which sense energy exchange parameters in a way to measurethe impedance of a region of the subject. In most embodiments,interfaces 120, 125 130, 135 will be electrodes adapted to exchangeelectrical energy with a human, although some optical element adapted toilluminate a human may also be possible. Typically, two of theinterfaces 120, 125 are used to force current flow from one point on thesubject to a second point on the subject. The other two interfaces 130,135 are used to measure the voltage across two points on the subject. Incertain circumstances, interfaces 130, 135 are contactless, e.g.capacitively coupled electrodes, interfaces used to sense the energyexchange parameters. It may be noted that the current application pointsand the voltage measurement points in these embodiments can be the same,adjacent to one another, or at significantly different locations.

Energy source 110 can be, e.g., an optical energy source or an electricenergy source. For example, energy source can be one or more alternatingand/or direct current and/or voltage source. Energy source 110 isconnected to inputs 120, 125 by leads 140, 145. Leads 140, 145 canconduct energy generated by source 110 for exchange with the portion ofthe organism coupled to main body 105. For example, leads 140, 145 canbe electrical wires capable of carrying an electric current for exchangewith the portion of the organism, or leads 140, 145 can be opticalwaveguides capable of carrying light for exchange with the portion ofthe organism followed by main body 105.

In one electrical embodiment, a sensing circuit 115 comprises adifferential amplifier connected to electrodes 120, 125 by leads 140,145 and to electrodes 130, 135 by leads 150, 155. Leads 140, 145 canconduct voltage across source 110 to amplifier 115. Leads 150, 155 canconduct voltage across electrodes 130, 135 as another input to theamplifier 115. Amplifier 115 can sense voltages across electrodes 130,135 and electrodes 120, 125 to generate one or more results 160. It willbe appreciated that amplifier 115 could be implemented as two or moreamplifiers that separately sense relative voltages across any desiredelectrode pairs. Current sensing could also be implemented to directlymeasure the current output from source 110.

In operation, main body 105 flexes to follow a portion of an organismand maintain inputs 120, 125 and outputs 130, 135 so that they canexchange energy with the followed portion. Source 110 generates one ormore types of energy that is conducted over leads 140, 145 throughinterfaces 120, 125 and exchanged with the followed portion of theorganism. In turn, interfaces 130, 135 sense one or more energy exchangeparameters from the followed portion. Sensing circuit 115 generates aresult 160 based on the sensed signals. Result 160 reflects, at least inpart, the hydration of the monitored organism.

Probe 100 can generate result(s) 160 continuously or intermittently overextended periods of time. For example, result 160 can be a subset of thecomparisons of the sensed parameters at interfaces 130, 135 with theamount of energy input at inputs 120, 125, or result 160 can be all suchcomparisons. For example, result 160 can be intermittent samples ofvoltages from the results of continuous application of a substantiallyconstant current. As another example, result 160 can be periodic (e.g.,every 5 to 30 minutes, such as every 10 minutes) results of successive,shorter duration current applications.

FIG. 2 shows one implementation of a probe for monitoring the hydrationof an organism, namely a bioelectric impedance spectroscopy probe 200.Bioelectric impedance spectroscopy is a measurement technique in whichthe electrical conductivity of all or a portion of an organism ismeasured. When the conductivity of the entirety of an organism ismeasured such as by passing current from one ankle to an opposite wristor between both hands, this can be referred to as whole body bioelectricimpedance spectroscopy. When the conductivity of a portion of anorganism is measured such as by a cluster of more locally placedelectrodes, this can be referred to as segmental (or regional)bioelectric impedance spectroscopy. In either case, the measuredelectrical conductivity can reflect the hydration of the measuredorganism or the measured portion of the organism.

Bioelectric impedance spectroscopy generally involves the exchange ofelectrical energy with the organism. The exchanged electrical energy caninclude both alternating current and/or voltage and direct currentand/or voltage. The exchanged electrical energy can include alternatingcurrents and/or voltages that alternate at one or more frequencies. Forexample, the alternating currents and/or voltages can alternate at oneor more frequencies between 100 Hz and 1 MHz, preferably at one or morefrequencies between 5 KHz and 250 KHz.

Different frequencies of electrical energy can be used to measureconductivity in different portions of the organism. For example, in someorganisms, lower frequency electrical energy may be conductedpreferentially through tissues having fewer membranous componentswhereas higher frequencies may be conducted through a larger variety oftissues. In many cases, it is advantageous to make impedancemeasurements at two or more different frequencies in the same region. Asexplained further below, DC measurements can help characterize impedanceover the skin surface. Thus, measurements at different frequencies madeby a single probe can provide information regarding both the amount anddisposition of water within a probed organism or within a probed portionof the organism.

Referring again to FIG. 2, bioelectric impedance spectroscopy probe 200includes a body 205, a current source 210, a digital-to-analog converter215, an amplifier 220, an analog-to-digital converter 225, a memory 230,and a controller 235. Body 205 is a flexible member that supports twoworking electrodes 245, 250 and two sensing electrodes 255, 260. Body205 can be flexible enough to follow a portion of the human body tomaintain electrodes 245, 250, 255, 260 in contact with that portion. Thefollowed portion can include skin surfaces, mucosal surfaces in themouth and/or nasal passages, and other body passages or orifices. Body205 can be sized to probe the conductivity of the entirety of anorganism and thus perform whole body bioelectric impedance spectroscopy.In some advantageous embodiments described in detail herein, body 205 issized to probe the conductivity of a portion of an organism and thusperform segmental bioelectric impedance spectroscopy.

Working electrodes 245, 250 can be adapted to conduct current through oralong the probed portion of the monitored organism. Sensing electrodes255, 260 can be adapted to measure the potential of locations in theprobed portion of the monitored organism. Electrodes 245, 250, 255, 260are generally electrically conductive in that their electrical impedanceis relatively small when compared to the electrical impedance of themonitored portion of an organism at the probed frequency. For example,electrodes 245, 250, 255, 260 can include metals, sintered metalliccomposites, conductive polymers, gels, carbon-based materials, siliconmaterials, electrically conductive microneedles, conductive solutions,or combinations thereof. In one implementation, electrodes 245, 250,255, 260 are electrically conductive adhesive gel electrodes such as theRED DOT electrodes available from 3M Corp. (St. Paul, Minn.).

Electrodes 245, 250, 255, 260 can be supported by body 205 on the outersurface of the skin of a monitored organism. Alternatively, electrodes245, 250, 255, 260 can be supported by body 205 beneath the skin of amonitored organism. For example, electrodes 245, 250, 255, 260 can besupported subdermally or electrodes 245, 250, 255, 260 can be supportedon transdermal elements such as microneedles that penetrate the skin.When placed on the skin surface, electrodes 245, 250, 255, 260 canadvantageously be each supported by body 205 at positions that areseparated from one another by more than approximately ten times thethickness of the skin. When hydration is monitored in humans, electrodes245, 250, 255, 260 that are above the skin can each generally besupported at positions that are separated from one another by more than2.5 millimeters. In one implementation, the distance between workingelectrodes 245, 250 is greater than 1 cm. For embodiments that include alocalized cluster of electrodes on one or more patches secured to theskin, the distance between electrodes is advantageously less than about25 cm so that the impedance measurement is focused regionally on thesubject. Such regional measurements have been found to produce usefuldata that can be generated and distributed with convenient apparatus.

In one implementation, working electrodes 245, 250 are different thansensing electrodes 255, 260. For example, working electrodes 245, 250can be larger than sensing electrodes 255, 260 and/or made fromdifferent materials. In other implementations, sensing electrodes 255,260 may be contactless electrodes, e.g. capacitively coupled electrodes(Quasar, San Diego, Calif.) while working electrodes 245, 250 arecontact-based electrodes, e.g. RED DOT electrodes.

Current source 210 is a source of alternating and/or direct electricalcurrent. As deployed in probe 200, current source 210 can driveelectrical current from working electrode 245 to working electrode 250through and/or along a monitored organism. In one implementation,current source 210 is capable of driving between 10 microamperes and 10milliamperes, preferably between 100 microamperes and 1 milliamperes, ofone or more frequencies of alternating and/or direct current through oralong electrical impedances characteristic of humans. Typically, currentis held at a known or measured substantially constant value, and voltageis measured to provide an impedance value. It is also possible to applya constant voltage and measure the amount of current. Digital-to-analogconverter 215 can be an integrated circuit or other electronic devicethat converts a digital signal into a corresponding analog signal. Asdeployed in probe 200, digital-to-analog converter 215 can convertdigital control signals from controller 235 into analog control signalsto control the output of electrical current from current source 210.

Amplifier 220 can be a differential voltage amplifier in that itamplifies a voltage difference on sensing electrodes 255, 260. Thisvoltage difference results from current source 210 driving electricalcurrent from working electrode 245 to working electrode 250 throughand/or along the monitored organism. Analog-to-digital converter 225 canbe an integrated circuit or other electronic device that converts thissensed voltage difference into a corresponding digital signal forreading by controller 235 and/or storage in memory 230.

Memory 230 can be a data storage device that can retain information inmachine-readable format. Memory 230 can be volatile and/or nonvolatilememory. For example, memory 230 can be a RAM device, a ROM device,and/or a memory disk.

Controller 235 is a device that manages the generation and flow of datain probe 200. Controller 235 can be hardware configured to performselect operations or a data processing device that performs operationsin accordance with the logic of a set of machine-readable instructions.In some implementations, controller can receive information related tothe management of the generation and flow of data in probe 200 via oneor more input devices. In some implementations, controller 235 canoutput information from probe 200 via one or more output devices. CustomASICs or gate arrays can be used, as well as commercially availablemicrocontrollers from, for example, Texas Instruments and Motorola.

The operations performed by controller 235 can include regulating thetiming of hydration measurements and the timing of the transmission ofhydration measurement results, logic operations, signal processing, anddata analysis. For example, data analysis can be used to determine thebioelectric impedance of portions of a monitored organism. For example,equivalent circuit impedance analysis in the time or frequency domaincan be performed. Instructions for performing such operations can bestored in a read only memory portion of memory 230, temporary valuesgenerated during such operations can be stored in a random accessportion of memory 230, and the results of operations can be stored in anon-volatile portion of memory 230.

In operation, current source 210 drives one or more frequencies ofalternating and/or direct current between working electrodes 245, 250and through the subject organism. Amplifier 220 buffers and amplifiesthe potential difference between sensing electrodes 255, 260.Analog-to-digital converter 225 converts this signal into a digital formthat can be received by controller 235 for storage at memory 230, asappropriate. In some implementations, controller 235 may control source210 to change the frequency and/or magnitude of current generated. Thecontrol of source 210 can be performed in light of the magnitude of thesignal(s) output by amplifier 220 and/or in light of instructionsreceived by controller 235 over one or more input devices.

FIG. 3 shows one implementation of a portable bioelectric impedancespectroscopy probe, namely a bandage (or “patch”) probe 300. Probe 300can be self-powered in that main body 205 includes (in addition toelectrodes 245, 250, 255, 260) a portable power source, such as abattery 305. Probe 300 is portable in that probe 300 can be moved from afixed location and is adapted to perform at least some of the signalgeneration and processing, control, and data storage functions ofcurrent source 210, a digital-to-analog converter 215, an amplifier 220,an analog-to-digital converter 225, a memory 230, and a controller 235without input from a fixed device. For example, probe 300 can be borneby the monitored organism. Circuitry 310 can be, e.g., an applicationspecific integrated circuit (ASIC) adapted to perform these functions.Circuitry 310 can also be a data processing device and/or one or moreinput/output devices, such as a data communication device.

Main body 205 also advantageously includes an adhesive 315. Adhesive 315can be adapted to adhere to the skin surface of the monitored organismand thereby maintain electrodes 245, 250, 255, 260 in contact with theportion of an organism followed by main body 205.

A portable probe 300 allows a monitored organism to be ambulatory whilehydration monitoring occurs. This allows for data collection to beextended beyond periods of confinement. Thus, hydration monitoring canbe continued while an organism participates in various activities atdifferent locations, over durations suitable for identifying the onsetof disease states.

FIGS. 4A and 4B respectively illustrate example deployments ofbioelectric impedance spectroscopy probe 200 and bandage probe 300 tomonitor hydration. FIG. 4A shows a pair of probes 200 deployed along asteering wheel 400 so that a driver's hands will come into intermittentelectrical contact with one or both of probes 200. During thisintermittent contact, the driver's hydration can be monitored.

FIG. 4B shows bandage probe 300 deployed to adhere to the torso ofperson 405. Bandage probe 300 is sized to probe the conductivity of aportion of person 405. In particular, bandage probe 300 adheres to thefront chest of person 405 with one end located in the vicinity of thexiphoid process. Bandage probe 300 extends axially and downward from thexiphoid process towards the lateral side of person 405.

This positioning of bandage probe 300 may facilitate the monitoring ofhydration in a body region or whole body to detect/monitor forhypovolemia, hemorrhage or blood loss.

FIGS. 5 and 6 show another implementation of a bioelectric impedancespectroscopy probe, namely a portable strap probe 500. Main body 205 ofstrap probe 500 is a strap or a belt that can form a loop to encirclethe body, or a portion of the body, of a monitored individual. Such anencirclement can maintain electrodes 245, 250, 255, 260 in contact withthe encircled portion. In addition to working electrodes 245, 250, twosets of sensing electrodes 255, 260, battery 305, and circuitry 310,main body 205 also includes a data communication device 505 having atransceiver 510. Data communication device 505 can be a wirelesscommunication device that can exchange information between circuitry 310and an external entity. Wireless data link 1125 can carry informationusing any of a number of different signal types includingelectromagnetic radiation, electrical signals, or acoustic signals. Forexample, data communication device 505 can be a radio frequencycommunication device. Transceiver 510 can be an assembly of componentsfor the wireless transmission and reception of information. Thecomponents can include, e.g., an RF antenna. The wirelessreceiver/transmitter circuitry can be made part of any embodimentdescribed herein.

The two sets of sensing electrodes 255, 260 can be used to measurehydration at different locations on a monitored individual. For example,when working electrodes 245, 250 drive current through and/or along thesurface of the encircled portion of a monitored individual, thepotential differences between all sensing electrodes 255, 260 can beused to gain information about the conduction of current in the vicinityof electrodes 255, 260. A measurement of multiple potential differencesbetween more than two sensing electrodes 255, 260 can also be used, e.g., to make cross measurements and ratiometric comparisons that can beused to monitor hydration while aiding in calibration and helping toaccount for measurement variability such as temperature changes, changesin the position of the monitored individual, and movement of strap probe500 over time.

FIGS. 7, 8A, 8B, 8C, 9A, and 9B illustrate example deployments ofimplementations of strap probe 500 to monitor hydration in a person 405.In FIG. 7, strap probe 500 is sized to encircle the torso of person 405and is deployed to probe the conductivity of the torso of person 405.Such a positioning of strap probe 500 may facilitate the monitoring ofhydration in the chest region, as well as the detection of pulmonaryedema, acute blood loss, systemic hemorrhage, hypervolemia orhyperhydration.

In FIG. 8A, strap probe 500 is sized to encircle the thigh of person 405and is deployed to probe the conductivity of the thigh of person 405.Such a positioning of strap probe 500 may facilitate the monitoring ofhydration in the underlying tissue, as well as the identification ofdisease states such as acute or chronic dehydration, acute blood loss,systemic hemorrhage, hypervolemia or hyperhydration.

In FIG. 8B, strap probe 500 is sized to encircle the lower leg of person405 and is deployed to probe the conductivity of the lower leg of person405. As shown, strap probe 500 encircles the ankle, but strap probe 500can also encircle the foot, the calf, or a toe to probe the conductivityof the lower leg. Such a positioning of strap probe 500 may facilitatethe monitoring of hydration in the underlying tissue, as well as theidentification of disease states such as congestive heart failure wherewater accumulates in the lower legs including pitting edema, acute bloodloss, systemic hemorrhage, hypervolemia or hyperhydration.

In FIG. 8C, strap probe 500 is sized to encircle the bicep of person 405and is deployed to probe the conductivity of the bicep of person 405.Such a positioning of strap probe 500 may facilitate the monitoring ofhydration in the underlying tissue, as well as the identification ofdisease states such as acute or chronic dehydration, acute blood loss,systemic hemorrhage, hypervolemia or hyperhydration.

In FIG. 9A, strap probe 500 is incorporated into a pair of pants 905 andsized to encircle the torso of person 405 to probe the conductivity ofthe torso of person 405. Incorporating a probe 500 into pants 905 mayreduce the intrusiveness of probe 500 and help ensure that a monitoredindividual deploys probe 500.

In FIG. 9B, strap probe 500 is incorporated into a sock 910 and sized toencircle the lower leg of person 405 to probe the conductivity of thelower leg of person 405. Incorporating a probe 500 into sock 910 mayreduce the intrusiveness of probe 500 and help ensure that a monitoredindividual deploys probe 500. In alternate implementations, such strapprobes may be incorporated into other articles such as shirts, sweatbands, or on-body devices for this monitoring purpose.

As discussed further below, in some deployments, multiple probes atdifferent locations may be used to monitor the hydration of a singleindividual. The measurement results from the different probes can becompared and correlated for calibration and error minimization. Othertechniques that measure biological parameters can also be used inconjunction with single or multiple probes. The biological parametermeasurements can be compared and correlated with the probe measurementsto calibrate the measurements and minimize the error associated with themeasurements. As one example, bioelectric impedance measurements madeusing a QUANTUM X body composition analyzer (RJL Systems, Inc., ClintonTwp., Mich.) and/or a Hydra 4200 bioimpedance analyzer (XitronTechnologies Inc., San Diego, Calif.) can be compared and correlatedwith probe measurements.

As another example, skin temperature measurements can be used inmonitoring the hydration of an individual. In general, skin surfacetemperature will change with changes in blood flow in the vicinity ofthe skin surface of an organism. Such changes in blood flow can occurfor a number of reasons, including thermal regulation, conservation ofblood volume, and hormonal changes. In one implementation, skin surfacemeasurements are made in conjunction with hydration monitoring so thatchanges in apparent hydration levels, due to such changes in blood flow,can be considered.

In some deployments, one or more probes can be moved to differentportions of a single individual over time to monitor the hydration ofthe individual. For example, a probe can monitor the hydration of anindividual at a first location (e.g., the torso) for a select period(e.g., between about 1 to 14 days, or about 7 days), and then the sameprobe can be moved to a different location (e.g., the thigh) to monitorthe hydration of the same individual for a subsequent time period. Suchmovement of a probe can extend the lifespan of a probe and increase thetype of information gathered by the probe. Further, movement of theprobe can minimize surface adhesion loss and any decrease in hygieneassociated with the monitoring.

The movement of a probe such as probe 500 to a new location on the body,or the attachment of a new probe at a different location, may result ina change in baseline impedance measurements even when the hydration ofthe monitored organism has not changed. A baseline measurement is astandard response to hydration monitoring. The standard response can beindicative of the absence of a disease state or of the absence ofprogression in a disease state. Changes in the baseline impedancemeasurements can result from changes in factors unrelated to a diseasestate. For example, changes in the baseline impedance measurements canresult from different skin thicknesses, body compositions, or otherdifferences between two locations. Measurements made at the differentlocations can be normalized to account for such differences in baselinemeasurements. Such a normalization can include adjustments in gainand/or adjustments in offset. Gain adjustments may be based on theabsolute value of the impedance measurement(s), the impedancedifference(s) observed at the old and the new locations, or combinationsthereof. Offset adjustments can generally be made after gain adjustmentsand can be based on absolute impedance values and/or other factors.Alternatively, analysis thresholds used to identify disease states canbe adjusted.

In some implementations, the monitored individual may be placed in anon-ambulatory state (e.g., supine and resting) in order to acquiredirectly comparable baseline measurements at different locations.Multiple probes need not be attached to the same organism in order tonormalize baseline measurements. For example, hydration measurementresults obtained using a first probe at a first location can be storedand compared with hydration measurement results obtained later using asecond probe at a second location. This can be done, e.g., when the timebetween the collection of the results at the first location and thecollection of the results at the second location is relatively short,e.g., less than 1 hr. If the replacement patch is not attached to thepatient within this period, comparison of bioelectric impedance valuesto other calibration standards, e.g., body weight and body weightchange, urine specific gravity, blood osmolality, can also be used forsuch comparisons.

FIG. 10A shows another implementation of a strap probe, namely a strapprobe 1000. In addition to electrodes 245, 250, 255, 260, battery 305,circuitry 310, data communication device 505, and transceiver 510, mainbody 205 also includes an output device 1005. Output device 1005 can bea visual display device (such as a light emitting diode or a liquidcrystal display), an audio output device (such as a speaker or awhistle), or a mechanical output device (such as a vibrating element).

In operation, output device 1005 can present information regarding thehydration monitoring to a monitored individual. The presentedinformation can be received by output device 1005 from circuitry 310 andcan indicate monitoring results and/or alerts. Monitoring results caninclude the current hydration state of an individual as well asindications that certain disease states, such as acute dehydration,acute blood loss, systemic hemorrhage, hypervolemia, hyperhydration,wound infection or cutaneous ulcers are present or imminent. Monitoringalerts can include indications of current or imminent apparatusmalfunction, such as loss of contact between any of electrodes 245, 250,255, 260 and the monitored individual, a lack of available memory, lossof a data communication link, or low battery levels.

FIG. 10B shows another implementation of a strap probe, namely a strapprobe 1010. In addition to electrodes 245, 250, 255, 260, battery 305,circuitry 310, data communication device 505, and transceiver 510, mainbody 205 also includes a skin temperature sensor 1015. Sensor 1015 canbe a temperature sensing element that senses temperature in rangesencountered on the skin surface of the monitored organism and/or heatflux sensor to provide insight into temperature beneath the skinsurface. Sensor 1015 can be, e.g., a thermister, a thermocouple, amechanical thermometer, heat flux sensor or other temperature-sensingdevice. This temperature sensor can be part of any probe embodimentdescribed herein.

In operation, sensor 1015 can present information regarding skin surfacetemperature to circuitry 310. The presented information can be used bycircuitry 310 to perform data analysis and other aspects of hydrationmonitoring. Circuitry 310 can also transmit all or a portion of thetemperature information to other devices using, e.g., data communicationdevice 505 and transceiver 510.

With measurements of hydration and temperature at in the same vicinityof an organism, changes in apparent hydration levels due to changes inskin surface blood flow can be identified and accommodated in dataanalyses.

FIG. 10C shows a graph 1020 of example hydration monitoring results thatwere obtained using a bioelectric impedance monitor and a skintemperature thermometer. Graph 1020 shows the observed impedance 1025 ofa region on the thigh of a monitored individual as a function of skintemperature 1030. Graph 1020 includes a pair of traces 1035, 1040. Trace1035 shows the impedance measured with an electrical energy input signalhaving a frequency of 20 kHz, whereas trace 1040 shows the impedancemeasured with an electrical energy input signal having a frequency of100 kHz.

Traces 1035, 1040 were obtained as follows. Four Red Dot electrodes (3MCorp., St. Paul, Minn.) were arrayed in a linear axial fashion upon thefront of a thigh of a 42 yr old male subject weighing 201.3 pounds. Thesubject reclined in a supine position for 30 minutes in a room atambient temperature (74° F.). The bioelectric impedance of the thigh at20 kHz and 100 kHz was then measured with the subject in the supineposition. The measured impedance of the thigh was 45.36 ohms at 20 kHzand 30.86 ohms at 100 kHz. The skin surface temperature of the thigh wasthen measured using an infrared thermometer (Thermoscan, Braun GmbH,Kronberg, Germany). The measured temperature was 89.0° F. The subjectthen jogged six miles, taking approximately 90 minutes. The subject wasthen weighed. The measured weight was 197.6 pounds, indicating a loss ofbody water of about 3.5 pounds, or about 1.7%. The subject then returnedto the supine position in the ambient temperature room. The bioelectricimpedance of the thigh at 20 kHz and 100 kHz was then measuredperiodically, as was skin surface temperature of the thigh.

Traces 1035, 1040 represent the results of these measurements.Initially, the measured bioelectric impedance at both 20 kHz and 100 kHzwas lower than before jogging and the measured temperature was higherthan before jogging. In other words, the measured bioelectric impedanceat both 20 kHz and 100 kHz decreased as skin temperature in the vicinityof the bioelectric impedance measurement increased.

The observed changes in skin temperature are believed to result, atleast in part, from local vasodilation as the body sheds excess heatgenerated during exercise. Such changes in vasodilation appear todecrease local impedance.

Over time, both the measured impedance and temperature moved in thedirection of the values observed before jogging. The movement showed alinear relationship between measured impedance and measured skintemperature at both 20 kHz and 100 kHz. This relationship can be used toaccommodate the impact of skin surface temperature on hydrationmonitoring results, as discussed further below. If desired, localvasodilation or vasoconstriction can be measured by other or additionalmethods such as with optical methods. A vasodilation parameter, whethermeasured or calculated via a temperature measurement or some other meansmay be used to correct absolute impedance measurements to appropriatelydetermine impedance changes over time due to hydration changes.

At the end of the recovery period, the measured impedance of the thighwas 50.27 ohms at 20 kHz and 34.30 ohms at 100 kHz, for a net increasein impedance of 4.91 ohms (10.8%) at 20 KHz and 3.44 ohms (11.1%) at 100KHz. Similar results have been observed with other subjects and othertest conditions.

This approximately 11% net increase in measured bioelectric impedance at20 kHz and 100 kHz is believed to reflect the water loss associated withthe observed decrease in body weight (i.e., the decrease of about 1.7%).

The measurement results in traces 1035, 1040 can be used by circuitry310 to perform data analysis and other aspects of hydration monitoring.For example, the impact of skin surface temperature on hydrationmonitoring results can be accommodated. In one example, the relationshipbetween bioelectric impedance and temperature illustrated by traces1035, 1040 can be used to compare hydration monitoring results obtainedat different skin surface temperatures. For example, with a skin surfacetemperature of 90.5° F., the measured impedance at 20 kHz was 47.9 ohms.In order to compare this impedance measurement with impedancemeasurements made at a skin surface temperature of 89° F., the measuredimpedance can be adjusted by taking the difference between the twotemperatures (i.e., 89° F. −90.5° F.) of −1.5° F. and multiplying thisdifference by the measured dependence of impedance at 20 kHz ontemperature (i.e., the slope of −1.8052) to generate an adjustment valueof 2.71 ohms. The adjustment value can be added to the impedance at 20kHz measured with a skin surface temperature of 90.5° F. (i.e.,47.9+2.71) to yield an impedance that is comparable with impedancemeasurements made at 20 kHz with a skin surface temperature of 89° F.(i.e., 50.6 ohms). As seen, this adjusted impedance is consistent withthe impedance actually measured at this skin surface temperature (i.e.,50.27 ohms).

Such combinations of skin surface temperature measurements and hydrationmonitoring results can be used to improve hydration monitoring. Forexample, bioelectric impedance measurements can be adjusted based onlocal skin surface temperature measurements made in the vicinity of theprobe. This can improve the predictive value of impedance measurements,even relative to whole body impedance measurements where impedancemeasurement that reflect the electrical impedance through the entirebody may not precisely correlate with temperature measurements made atone or two body locations.

Factors unrelated to hydration may influence local skin surfacetemperature measurements. These factors include the rate of convectivecooling, the wind velocity, the presence of thermal insulation such asclothing, and ambient temperature gradients. Such factors that tend toinfluence heat exchange between the portion of the body of interest andthe environment may be accounted for directly (e.g., using additionaltemperature or humidity sensors) or indirectly (e.g., using standardtables and known values applied to parameters such as the thickness ofinsulating clothing). The accounting for such factors can includeadjustments to the local temperature used to compare hydrationmonitoring results.

In some implementations, hydration monitoring results obtained atportions of a monitored organism that have a known temperaturerelationship with another portion where skin surface measurement(s) aremade can be adjusted based on that known relationship. Also, otherfactors including weight, height, age, general fitness level, degree ofexertion, time of day, stage in a hormonal cycle, and gender can also beused to adjust hydration monitoring results and improve the predictivevalue of such results.

FIG. 11 shows a system 1100 for monitoring the hydration of an organism.System 1100 includes one or more probes 100 along with one or more datacollection apparatus 1105, a data management system 1110, aninput/output device 1115, and a data storage device 1120. Probe 100includes a wireless data communication device 505 that is capable ofestablishing a wireless data link 1125 with data collection apparatus1105. Wireless data link 1125 can transmit data using any of a number ofdifferent signals including electromagnetic radiation, electricalsignals, and/or acoustic signals. When probe 100 is subdermal, data link1125 can be a transdermal link in that data link 1125 conducts dataalong a path through the skin.

The data communicated along wireless data link 1125 can include a probeidentifier. A probe identifier is information that identifies probe 100.Probe 100 can be identified, e.g., by make or model. Probe 100 can alsobe identified by a unique identifier that is associated with a singleindividual probe 100. The probe identifier can include a serial numberor code that is subsequently associated with data collected by probe 100to identify that this data was collected by probe 100. In someembodiments, each individual electrode, or a patch or strap containing aset of electrodes incorporates an integrated circuit memory having astored unique or quasi-unique electrode/patch identifier. An interfacebetween the patch or electrodes and the communication device 505 can beimplemented so that the communication device 505 can send electrode orpatch identifiers as well as a separate identifier for the otherelectronics coupled to the patch. In this way, different parts of theprobe can be separately replaced, while still allowing complete trackingof the physical data generation, analysis, and communication apparatusused to gather all impedance data.

The data communicated along wireless data link 1125 can also includemessages to probe 100. Example messages include commands to changemeasurement and/or data analysis parameters and queries regarding thestatus and/or operational capabilities of the probe. Data communicationalong wireless data link 1125 can also include information related tothe initialization and activation of probe 100. Initialization caninclude the communication of a probe identifier to data collectionapparatus 1105. Initialization can also include the commencement ofmeasurement activities including, e.g. the start of an internal clockthat regulates the timing of hydration measurements and the transmissionof hydration measurement results. Such data communication can beconducted as an ongoing dialogue with data collection apparatus 1105.

Data collection apparatus 1105 is a device that generally supplementsprobe 100 by including components and/or features that complement thecomponents and/or features of probe 100. For example, such components orfeatures may be too large, too memory intensive, require toosophisticated data processing, and/or only be used too intermittently tobe included on probe 100. FIG. 12 shows one implementation of a datacollection apparatus 1105. Data collection apparatus 1105 can be aportable device in that data collection apparatus 1105 can be moved froma fixed location and perform at least some functions without input froma fixed device. For example, data collection apparatus 1105 can be ahandheld device that can be borne by a monitored individual.

Data collection apparatus 1105 includes a local user input portion 1205,a local user output portion 1210, a wireless data communication portion1215, and a wired data communication portion 1217 all arranged on a body1220. Local user input portion 1205 includes one or more components thatreceive visual, audio, and/or mechanical input from a user in thevicinity of data collection apparatus 1105. For example, local userinput portion 1205 can include a keypad 1225 and a mode selection button1230. Keypad 1225 can receive alphanumeric input from a user. Modeselection button 1230 can receive an operational mode selection from auser. The operational modes of data collection apparatus 1105 arediscussed further below.

Local user output portion 1210 includes one or more components thatprovide visual, audio, and/or mechanical output to a user in thevicinity of data collection apparatus 1105. For example, local useroutput portion 1210 can include a display panel 1235. Display panel 1235can be, e.g., a liquid crystal display screen. Display panel 1235includes various regions that display specific information to a localuser. In particular, display panel 1235 includes a battery chargedisplay region 1240, an operational mode display region 1245, atime/date display region 1250, a measurement result display region 1255,and an alert display region 1260.

Battery charge display region 1240 includes a graphical device thatindicates the charge remaining on a battery or other power element thatpowers data collection apparatus 1105. Operational mode display region1245 includes a text list of the various operational modes of datacollection apparatus 1105. The listed operational modes include a testmode, a set-up mode, a synchronization mode, and a measurement mode. Thetext indicating measurement mode (i.e., “MEAS”) includes an indicium1265 that indicates that the current operational mode of data collectionapparatus 1105 is the measurement mode. Time/date display region 1250includes text indicating the current time and date. Measurement resultdisplay region 1255 includes text and/or graphical elements thatindicate the result(s) of a hydration measurement made by one or moreprobes 100. Alert display region 1260 includes a text and/or graphicalwarning that the probe measurement results are indicative of one or moredisease states being present or imminent. Alert display region 1260 canalso indicate that a malfunction of probe 100 and/or data collectionapparatus 1105 is occurring or imminent.

Wireless data communication portion 1215 can include a first wirelesscommunication transceiver 1265 and a second wireless communicationtransceiver 1270. Transceivers 1265, 1270 can be separate devices ortransceivers 1265, 1270 can include common components for the wirelesscommunication of data. For example, transceivers 1265, 1270 can eachinclude a separate RF antenna.

Transceivers 1265, 1270 can be dedicated to the exchange of data with aparticular device, or a particular class of devices. For example,transceiver 1265 can be dedicated to the exchange of data with one ormore probes 100 over one or more wireless data links 1125, whereastransceiver 1270 can be capable of exchanging data with other datacollection apparatus and/or with one or more data management systems1110. Transceivers 1265, 1270 can function with cellular communicationnetworks, alpha-numeric paging networks, WiFi or other systems for thewireless exchange of data.

Wired data communication portion 1217 can include one or more connectorports 1274 adapted to receive a plug or other terminal on one or morewired data links. The wired data links can be capable of exchanging datawith other data collection apparatus and/or with one or more datamanagement systems 1110. The wired data link can be an optical data linkand/or an electrical data link. Electrical data links can be analog ordigital. The data links can operate in accordance with datacommunication protocols such as the TCP/IP suite of communicationsprotocols.

Body 1220 can be sealed to isolate electrical and other components (notshown) that perform operations such as driving portions 1205, 1210,1215, 1217 from the ambient environment. Body 1220 can be sized and thecomponents selected to allow data collection apparatus 1105 to beself-powered by an internal power supply (not shown). For example, datacollection apparatus 1105 can be powered by an internal rechargeablebattery. The components can be, e.g., data storage devices, dataprocessing devices, data communication devices, and driving circuitryfor managing the input and output of data from data collection apparatus1105.

Body 1220 can be designed to operate as an independent unit as shown orbody 1220 can be designed to integrate with separate communicationdevices. For example, body 1220 can be designed to integrate with acellular phone or personal data assistant to form all or a portion ofwireless data communication portion 1215.

Returning to FIG. 11, system 1100 can include a wired data link 1130and/or a wireless data link 1135 for the exchange of data between datacollection apparatus 1105 and data management system 1110. Wired datalink 1130 can terminate at a connector port 1274 on data collectionapparatus 1105, and wireless data link 1135 can terminate at transceiver1270 on data collection apparatus 1105.

Wireless data link 1125, wired data link 1130 and wireless data link1135 can exchange data in accordance with one or more communicationprotocols. The communication protocols can determine the format of thetransmitted information and the physical characteristics of thetransmission. Communication protocols can also determine data transfermechanisms such as synchronization mechanisms, handshake mechanisms, andrepetition rates. The data structures of the protocol may impact therate of data transfer using the protocol. Data can be organized inblocks or packets and transmissions can be made at specified intervals.For example, a transmission block can include synchronization bits, anaddress field that includes information identifying the data source, adata field containing the hydration monitoring data, and a checksumfield for testing data integrity at the receiver. The length of a datablock can vary, e.g., to reduce power consumption and increase devicelifetime. The same data can be transmitted multiple times to ensurereception.

In one implementation, exchanged data is organized in packets thatinclude four sections, namely, a header section, a 64 bit addresssection that includes a probe identifier identifying a probe 100 (and/oran electrode or electrode set identifier), an encrypted data section,and a check-sum or error correction section. The data section can beencrypted using an algorithm that relies upon the address section.

Probe 100, data collection apparatus 1105, and data management system1110 can all confirm a successful exchange of data using a confirmationsuch as an electronic handshake. An unsuccessful exchange of data can bedenoted by transmission of an error message, which can be responded toby a retransmission of the unsuccessfully exchanged data.

In some implementations, probe 100, data collection apparatus 1105, anddata management system 1110 can exchange data at a number of differentfrequencies. For example, when system 1100 includes multiple datacollection apparatus 1105, each data collection apparatus 1105 cantransmit data over wireless data link 1135 using a different frequencycarrier. As another example, when system 1100 includes multiple probes100, each probe 100 can transmit data over wireless data link 1125 usinga different frequency carrier. It will be appreciated that a variety ofmultiple access techniques such as time or code division, could bealternatively used.

The data communicated along wireless data link 1125, wired data link1130, and wireless data link 1135 can be encrypted in whole or in part.The encryption can be symmetric or asymmetric. The encryption can relyupon encryption keys based on the probe identifier or on alphanumericcodes transmitted with the encrypted data. The encryption may beintended to be decrypted by a specific probe 100, a specific datacollection apparatus 1105, or a specific data management system 1110. Inone implementation, data communicated along wired data link 1130 isencrypted using 128 bit encryption at the SSL layer of the TCP/IPprotocol.

Both proprietary and public protocols can be used to exchange databetween probe 100, data collection apparatus 1105, and data managementsystem 1110. For example, the global system for mobile communications(GSM), Bluetooth, and/or the internet protocol (IP) can be used.

In one implementation, wireless link 1125 is a spread-spectrum RF signalat wireless medical band frequencies such as the Medical ImplantCommunications Service (MICS) (400-406 MHz) or the Wireless MedicalTelemetry Service (WMTS) (609-613 MHz and 1390-1395 MHz).

Data management system 1110 is a data processing device that conductsoperations with the data collected by probe 100 that relates tohydration of the organism. The operations can be conducted in accordancewith the logic of instructions stored in machine-readable format. Theconducted operations can include the processing of such data, thedisplay of such data, and the storage of such data.

Data management system 1110 can be remote from data collection apparatus1105 in that data management system 1110 need not be part of a localdata communication network that includes data collection apparatus 1105.For example, data management system 1110 can be a data processingapparatus that is accessible by one or more medical personnel.

The processing of data by data management system 1110 can include dataanalysis to identify disease states in monitored organisms or problemswith the monitoring. For example, data management system 1110 canperform impedance analysis using model equivalent circuits to determinehydration levels at different locations in a monitored organism.

The display of data by data management system 1110 can include therendition of the results of hydration monitoring on one or moreinput/output devices 1115. Input/output device 1115 can include visual,auditory, and/or tactile display elements that can communicateinformation to a human user (such as medical personnel). For example,input/output device 1115 can include a monitor, a speaker, and/or aBraille output device. Input/output device 1115 can also include visual,auditory, and/or tactile input elements such as a keyboard, a mouse, amicrophone, and/or a camera. Input/output device 1115 can thus rendervisual, auditory, and/or tactile results to a human user and thenreceive visual, auditory, and/or tactile input from the user.

The storage of data by data management system 1110 can include thestorage of the results of hydration monitoring on one or more datastorage devices 1120 that retain information in machine-readable format.Data storage devices 1120 can include volatile and/or nonvolatilememory. For example, data storage devices 1120 can be a RAM device, aROM device, and/or a memory disk.

In operation, all or some of the constituent components of system 1100can operate in one or more operational stages. For example, during atest stage, the constituent components of system 1100 can testthemselves to determine that they are functional. For example, probe 100and data collection apparatus 1105 can confirm that they are capable ofexchanging data along link 1125, and data collection apparatus 1105 anddata management system 1110 can confirm that they are capable ofexchanging data along one or more of links 1130, 1135. As anotherexample, probe 100 can confirm that inputs 120, 125 and outputs 130, 135are properly positioned relative to a monitored organism. For example,when inputs 120, 125 and outputs 130, 135 are electrodes 245, 250, 255,260, probe 100 can confirm that electrodes 245, 250, 255, 260 are inelectrical contact with the followed portion of the monitored organism.

During a setup stage, parameters relating to the monitoring of thehydration of an individual can be arranged. For example, a probe 100 candetermine the baseline measurement result for a given hydration level ina portion of a monitored organism and adjust monitoring parametersaccordingly. For example, the input signal level can be increased toaccommodate dry skin and high transdermal impedances. Data collectionapparatus 1105 can receive user input over one or more of local userinput portion 1205, wireless data communication portion 1215, and wireddata communication portion 1217. The received input can identifymonitoring parameters that are to be adjusted, such as the level atwhich an alert is to be sounded at probe 100 and/or data collectionapparatus 1105. Data management system 1110 can also receive user inputrelating to the arrangement of monitoring parameters. For example, datamanagement system 1110 can receive input from medical personnel overinput/output device 1115 indicating that hydration measurement resultsare to be transmitted by probe 100 to data collection apparatus overlink 1125 once every four hours. This timing parameter can be relayedfrom data management system 1110 over link 1130 to data collectionapparatus 1105 which relays the timing parameter over wireless link 1125to probe 100.

Parameters relating to the communication of information over one or moreof links 1125, 1130, 1135 can also be arranged during a setup stage. Forexample, the constituent components of system 1100 can selectcommunication protocols or parameters for communication protocols.

During a synchronization stage, clocks in two or more of probe 100, datacollection apparatus 1105, and data management system 1110 aresynchronized to enable synchronous data transmission along one or moreof links 1125, 1130, 1135. For example, in one implementation, datacollection apparatus 1105 transmits synchronization characters to datamanagement system 1110 over wired data link 1130. Data management system1110 can receive the synchronization characters and compares thereceived characters with a synchronization pattern. When the receivedcharacters correspond sufficiently with the synchronization pattern,data management system 1110 can exit the synchronization stage andexchange other data synchronously with data collection apparatus 1105over link 1130. Such a synchronization process can be repeatedperiodically.

In one implementation, data collection apparatus 1105 can receive and/ordisplay a serial number or other identifier of a synchronized probe 100.

During a measurement stage, one or more probes 100 can collect datarelating to the hydration of one or more monitored individuals. Theprobes 100 can perform data processing on the collected data, includingbioelectric impedance data analysis, filtering, and, eventidentification. In certain implementations, probes 100 can displaymeasurement values and/or assessments of hydration status.

The probes 100 can transmit data relating to the hydration monitoring(including results of processing and analyzing collected data) to one ormore data collection apparatus 1105. The transmitted data can include aprobe identifier that identifies the transmitting probe 100. Thetransmitted data can be encrypted.

Data collection apparatus 1105 can receive the data transmitted fromprobe 100 and update local user output portion 1210 based on thereceived data. The updating can include indicating, in operational modedisplay region 1245, that probe 100 is monitoring hydration, displaying,in measurement result display region 1255, recent monitoring results,and generating, in alert display region 1260, an alert to a user who islocal to data collection apparatus 1105. The alert can indicate, e.g.,that a monitored individual is suffering from one or more disease statesor that monitoring has somehow become impaired.

Data collection apparatus 1105 can also command one or more probes 100to transmit data relating to the hydration monitoring over link 1125.For example, data collection apparatus 1105 can transmit a query toprobe 100. The query can request that probe 100 provide informationregarding some aspect of the hydration monitoring. For example, a querycan request that probe 100 transmit a confirmation that hydrationmonitoring is occurring over link 1125, a query can request that probe100 transmit a recent measurement result over link 1125, or a query canrequest that probe 100 transmit one or more events of a particularcharacter over link 1125. Data collection apparatus 1105 can transmitqueries to probe 100 periodically, e.g., every hour or two.

Data collection apparatus 1105 can also relay some or all of the datatransmitted from probe 100 to data management system 1110. The data canbe relayed over one or more data links 1130, 1135. Data collectionapparatus 1105 can relay such data directly, i.e., without performingadditional analysis on the information, or data collection apparatus1105 can perform additional processing on such before relaying a subsetof the data to data management system 1110. Data collection apparatus1105 can notify a local user that data has been relayed by displaying adata relay notice on local user output portion 1210. Alternatively, datacan be relayed by data collection apparatus 1105 without notification toa local user.

Data collection apparatus 1105 can also receive user input over one ormore of local user input portion 1205, wireless data communicationportion 1215, and wired data communication portion 1217. The receivedinput can identify that data collection apparatus 1105 is to transmitdata to one or more probes 100 over link 1125. For example, the receivedinput can identify that data collection apparatus 1105 is to instructprobe 100 to generate an alarm signal indicating that a monitored personsuffers under a disease state. As another example, the received inputcan identify that data collection apparatus 1105 is to transmit a queryto a probe 100 over wireless link 1125. As another example, the receivedinput can identify that data collection apparatus 1105 is to transmit aninstruction instructing probe 100 to change a parameter of the hydrationmonitoring, including one or more threshold values for identifying adisease state.

Data collection apparatus 1105 can also perform data processing andstorage activities that supplement the data processing and storageactivities of probe 100. For example, data collection apparatus 1105 canperform more extended data analysis and storage, including signalprocessing and analysis. For example, data collection apparatus 1105 canperform impedance analysis using model equivalent circuits to determinehydration levels at different locations in a monitored organism. Asanother example, data collection apparatus 1105 can perform trendinganalyses that identify a general tendency of hydration levels to changeover extended periods of time, or data collection apparatus 1105 canperform comparisons between hydration levels obtained using multipleprobes 100. The multiple probes 100 can monitor the hydration of asingle organism, or the multiple probes can monitor the hydration ofmultiple organisms. Data collection apparatus 1105 can compare andcorrelate monitoring results from multiple probes to calibrate one ormore probe 100 and minimize errors during monitoring.

Data collection apparatus 1105 can also compare and/or correlate theresults of hydration monitoring with the results of monitoring otherbiological parameters. For example, data collection apparatus 1105 cancompare and correlate the results of hydration monitoring with theresults of heart monitoring, drug delivery schedules, and temperaturemonitoring. Data collection apparatus 1105 can receive the othermonitoring results over one or more of local user input portion 1205,wireless data communication portion 1215, and wired data communicationportion 1217. For example, data collection apparatus 1105 can receivethe other monitoring results over one or more of links 1125, 1130, 1135.

Data collection apparatus 1105 can also exchange data with other devicesand systems (not shown in FIG. 11). For example, data collectionapparatus 1105 can receive other monitoring results directly from othermonitoring instruments. As another example, data collection apparatus1105 can transmit data relating to the results of hydration monitoringto other local or remote parties. The other parties can be externalentities in that they do not share a legal interest in any of theconstituent components of system 1100. For example, the other partiescan be a medical group that has contracted with an owner of system 1100to monitor hydration of an individual.

Data management system 1110 can receive the results of hydrationmonitoring from data collection apparatus 1105 over one or both of datalink 1130, 1135. The received results can include analyses of thehydration of an organism, as well as comparisons and correlations ofmonitoring results from multiple organisms or other biologicalparameters.

Data management system 1110 can conduct operations with the receiveddata, including processing the data to identify disease states andproblems with the monitoring. For example, data management system 1110can perform impedance analysis using model equivalent circuits todetermine hydration levels at different locations in a monitoredorganism. As another example, data management system 1110 can performtrending analyses that identifies a general tendency of hydration levelsto change over extended periods of time, or data management system 1110can perform comparisons between hydration levels obtained using multipleprobes 100. The multiple probes 100 can monitor the hydration of asingle organism, or the multiple probes can monitor the hydration ofmultiple organisms. Data management system 1110 can compare andcorrelate monitoring results from multiple probes to calibrate one ormore probe 100 and minimize errors during monitoring. Data managementsystem 1110 can also perform analyses that require hydration monitoringresults from statistically significant numbers of organisms. Suchanalyses can include billing assessments, geographic assessments,epidemiological assessments, etiological assessments, and demographicassessments.

Data management system 1110 can render the results of hydrationmonitoring on one or more input/output devices 1115 and store theresults of hydration monitoring on one or more data storage devices1120. Data management system 1110 can also provide the results of thedata processing to data collection apparatus 1105 and/or probe 100 overdata links 1125, 1130, 1135. The provided results can include anindication that a disease state is present and/or an indication thatprobe 100 should generate an alarm signal indicating that a monitoredorganism suffers under a disease state. Data management system 1110 canalso provide such indications to external entities, including medicalpersonnel interacting with input/output device 1115 and medicalpersonnel in the vicinity of the monitored organism. For example, anemergency medical technician (EMT) can be informed that a monitoredindividual in the EMT's vicinity suffers from acute dehydration. Asanother example, data management system 1110 can also post an indicationin an external system such as the clinical information system of ahealthcare organization or an Internet portal.

In one implementation, data management system 1110 can request, fromdata collection apparatus 1105 and/or probe 100, that additionalmonitoring activities be performed. The request can be spurred by theresults of analyses performed at data collection apparatus 1105 and/orthe analyses performed at data management system 1110. The request canalso be spurred by a human user such as medical personnel interactingwith input/output device 1115. The requests can be based on the resultsof hydration monitoring. The additional monitoring activities can bedirected to other biological parameters, or the additional monitoringactivities can be directed to gaining more information about thehydration of the monitored individual. For example, data managementsystem 1110 can identify surveys and/or survey questions that are to bepresented to a monitored organism to facilitate hydration monitoring. Asurvey is a series of questions designed to gather information about thehydration of a monitored organism. A survey is generally presented to amonitored organism, but a survey can also be presented to individualshaving contact with the monitored organism. A survey can be presented,e.g., over a telephone or through the mail. Survey and survey questionscan be generated before monitoring begins and stored, e.g., at probe100, data collection apparatus 1 105, and/or data management system1110.

Survey questions can be directed to ascertaining, e.g., body position ofa monitored organism, length of time that the monitored organism hasbeen in one position, the diet of the monitored organism, the activitylevel of the monitored organism, or the time zone of the monitoredorganism. Example survey questions include “Are you currentlyexercising?”, “Did you remove the probe?”, and “Have you recently takena diuretic?” The questions presented during a survey can depend upon theresponses to previous questions. For example, if a monitored individualhas removed probe 100, subsequent questions can be deleted.

Responses to the questions in the survey can be received using, e.g., aninteractive voice recognition system (IVRS) or keypad entry on a touchtone phone. Data management system 1110 can present the survey itself ordata management system 1110 can direct another system to present thesurvey. The responses to survey questions can be scored based upon apredetermined criteria set and used in further analyses in hydrationmonitoring.

FIG. 13 shows another implementation of a system for monitoring thehydration of an organism, namely a system 1300. In addition to one ormore data collection apparatus 1105, data management system 1110,input/output device 1115, and data storage device 1120, system 1300includes a collection of multiple probes 100, 1305, 1310, 1315.Together, probes 100, 1305, 1310, 1315 form a data “hopping” network1317 in which data can be transferred amongst probes 100, 1305, 1310,1315. In particular, in network 1317, probe 1305 exchanges data withprobe 100 over a wireless data link 1320. Probe 1310 exchanges data withprobe 1305 over a wireless data link 1325. Probe 1315 exchanges datawith probe 1310 over a wireless data link 1330. The data exchangedamongst probes 100, 1305, 1310, 1315 over data links 1320, 1325, 1330can include hydration monitoring results, biological parametermonitoring results, queries, parameter change commands, encryption keys,probe identifiers, handshakes, surveys, and other information.

Such a “hopping” network 1317 may extend the range and robustness ofdata communication in system 1300.

FIG. 14 shows another implementation of a system for monitoring thehydration of an organism, namely a system 1400. In addition to one ormore data collection apparatus 1105, data management system 1110,input/output device 1115, and data storage device 1120, system 1400includes a pharmaceutical dispenser 1405. Pharmaceutical dispenser 1405is a device that provides compositions for ameliorating a disease stateof an individual. Pharmaceutical dispenser 1405 can provide such acomposition to an individual automatically (i.e., without humanintervention) or pharmaceutical dispenser 1405 can provide such acomposition in conjunction with the efforts of one or more individuals.For example, pharmaceutical dispenser 1405 can be an implantedcontrolled-release drug delivery device or pharmaceutical dispenser 1405can be a pill dispenser that is accessible by a monitored individual orby medical personnel.

Pharmaceutical dispenser 1405 includes a communications element 1410.Communications element 1410 can place dispenser 1405 in datacommunication with the constitutent components of system 1400. Forexample, in one implementation, communications element 1410 canestablish a wireless data link 1415 between dispenser 1405 and datacollection apparatus 1105.

In operation, pharmaceutical dispenser 1405 can receive data such asdispensation instructions from the constitutent components overcommunications element 1410. For example, when one or more of probe 100,data collection apparatus 1105, and data management system 1110identify, based at least in part on the results of hydration monitoring,that a monitored individual suffers under one or more disease states,pharmaceutical dispenser 1405 can receive instructions over element 1410that instruct dispenser 1405 to provide a composition to the monitoredindividual that ameliorates the identified disease state.

In response to the receipt of dispensation instructions, pharmaceuticaldispenser 1405 can provide a composition for ameliorating a diseasestate to the monitored individual. For example, pharmaceutical dispenser1405 can release a drug into the monitored individual's body orpharmaceutical dispenser 1405 can prepare a dosage of medicine for themonitored individual. The dispensation of a composition bypharmaceutical dispenser 1405 can be recorded at one or more memorydevices in system 1400, e.g., for use in analyzing the results ofhydration monitoring.

Probe 100 can communicate with data collection apparatus 1105 by a wireddata link. Both probe 100 and data collection apparatus 1105 can beincorporated into other items or equipment such as a vehicle, a radiounit, a shoe, football equipment, fire fighting equipment, gloves,hydration systems, bicycle handlebars, and other devices. Datacommunication along data link 1125 can be asynchronous, and the synchoperational mode eliminated from data collection apparatus 1105.

As shown in FIG. 15, multiple probes (i.e., probes 500 and 500′) can bedeployed at different locations at an organism 405 to monitor thehydration of the organism. In particular, strap probe 500 is sized toencircle the thigh of person 405 and is deployed to probe theconductivity of the thigh of person 405, whereas strap probe 500′ issized to encircle the lower leg of person 405 and is deployed to probethe conductivity of the lower leg of person 405.

The measurement results from the probes 500, 500′ can be compared andcorrelated for calibration and error minimization. For example, probe500′ can provide hydration measurement results that are used to identifydisease states such as congestive heart failure where water accumulatesin the lower legs, and probe 500 can provide hydration measurementresults that are used to calibrate the hydration measurement resultsobtained using probe 500′. Such a calibration can include makingdifferential measurements that accommodate variation in the hydrationmonitoring results that is unrelated to cardiac failure.

FIG. 16 shows an implementation of a system that uses multiple probesfor monitoring the hydration of an organism, namely a system 1700. Inaddition to one or more data collection apparatus 1105, data managementsystem 1110, input/output device 1115, and data storage device 1120,system 1700 includes probes 500, 500′. Probes 500, 500′ can be deployedon a single organism 405 as shown in FIG. 16. Probes 500, 500′ can bothestablish wireless data links 1125 with data collection apparatus 1105to communicate information used in hydration monitoring.

FIG. 17 shows an example of a model equivalent circuit 1500 that can beused in monitoring the hydration of an organism. In particular, modelequivalent circuit 1500 that can be used to model the electricalconductivity of an organism. Circuit 1500 models the impedances observedin bioelectric impedance spectroscopy using a probe 200 that supportselectrodes 245, 250, 255, 260 above a skin surface 1505 of an organism1510.

Model circuit 1500 includes a series of surface impedances 1515, 1520,1525, a series of transdermal impedances 1530, 1535, 1540, 1545, and aseries of subdermal impedances 1550, 1555, 1560. Surface impedances1515, 1520, 1525 can model the surface electrical impedances between therelevant of electrodes 245, 250, 255, 260. Surface impedances 1515,1520, 1525 can model both the conductivity through the surface of theskin and the conductivity through sweat and other conducting fluids onthe surface of the skin. In one implementation, surface impedances 1515,1520, 1525 are modeled as non-reactive (i.e., resistive) elements.

Transdermal impedances 1530, 1535, 1540, 1545 can model the electricalimpedances through the skin of a monitored organism. Transdermalimpedance 1530 includes a resistive component 1565 and a reactivecomponent 1570. Transdermal impedance 1535 includes a resistivecomponent 1575 and a reactive component 1580. Transdermal impedance 1540includes a resistive component 1585 and a reactive component 1590.Transdermal impedance 1545 includes a resistive component 1595 and areactive component 1597. Reactive components 1570, 1580, 1590, 1597 canmodel the electrical impedance through dense cellular layers as acapacitive element, whereas resistive components 1565, 1575, 1585, 1595can model the electrical impedance through hydrated and other portionsof the skin as a resistive element.

Subdermal impedances 1550, 1555, 1560 can model electrical impedancesthrough a monitored organism. For example, subdermal impedances 1550,1555, 1560 can model the electrical impedances of a portion of themonitored organism as a resistive volume conductor bounded by the skin.

In one implementation, in bioelectric impedance spectroscopy, probe 200supports electrodes 245, 250, 255, 260 above skin surface 1505. Currentsource 210 can drive electrical current between electrodes 245, 250. Thedriven current can include both direct current and alternating currentcomponents. The potential at electrodes 245, 250, 255, 260 providesinformation about the net impedance across equivalent circuit 1500 aswell as the impedance of different paths across equivalent circuit 1500.

For example, when direct current is driven across circuit 1500, a largeportion of the direct current will pass through surface impedances 1515,1520, 1525. Potential measurements at electrodes 245, 250, 255, 260under direct current application can be used to estimate the impedanceof surface impedances 1515, 1520, 1525. When certain frequencies ofalternating current are driven through circuit 1500, some portion of thealternating current can pass through surface impedances 1515, 1520,1525, transdermal impedances 1530, 1535, 1540, 1545, and subdermalimpedances 1550, 1555, 1560. Potential measurements at electrodes 245,250, 255, 260 can be used to estimate impedances 1515, 1520, 1525, 1530,1535, 1540, 1545, 1550, 1555, 1560. Such estimations can be made inlight of the estimations of surface impedances 1515, 1520, 1525 madeusing direct current.

The impact of various factors on the electrical conductivity of anorganism can be accommodated by changing the mathematical analysis ofmodel circuit 1500 or by changing aspects of data collection. Forexample, when surface impedances 1515, 1520, 1525 are particularly low,e.g., due to heightened conductivity through sweat or other conductingfluids on the surface of the skin, the measured potentials at electrodes245, 250, 255, 260 can be mathematically corrected to accommodate thelowered conductivity. For example, previously obtained surface impedanceestimates can be used to estimate the effect that changes in surfaceimpedances 1515, 1520, and 1525 have on the total impedance measurement,and thus isolate the change in sub-dermal impedance so as to moreaccurately monitor changes in subdermal tissue hydration. Alternatively,bioelectric spectroscopy measurements can be delayed altogether or probe200 can output an indication to a monitored individual that theindividual should dry the measurement region.

Model equivalent circuit 1500 can be used in conjunction with customapproaches to data analysis for monitoring the hydration of an organism.Such data analysis approaches can be used to interpret monitoring dataand to identify changes in the amount and distribution of water in amonitored organism. Data analysis approaches can also be used toincorporate results of other bioparameter measurements and responses tosurvey questions into the hydration monitoring.

Data analysis approaches can be performed in accordance with the logicof a set of machine-readable instructions. The instructions can betangibly embodied in machine-readable format on an information carrier,such as a data storage disk or other memory device. The instructions canalso be embodied in whole or in part in hardware such as microelectroniccircuitry.

Data analysis approaches can yield analysis results that can bedisplayed to a human user. The human user can be the monitoredindividual or another individual, such as a medical professional. Theanalysis results can be displayed in response to a prompt from the useror automatically, i.e., without user input. For example, the analysisresults can be displayed automatically when hydration indicative of adisease state is identified. When hydration monitoring is performedusing a system 1100, analysis results can be displayed at a probe 100,at a data collection apparatus 1105, and/or at a data management system1110 (FIGS. 11, 13, 14). Analysis results can be displayed using otheroutput devices such as the postal service, facsimile transmission, voicemessages over a wired or wireless telephone network, and/or the Internetor other network-based communication modalities.

Data analysis can be performed continuously or intermittently overextended periods of time. The analyzed data can be measurement resultscollected continuously or intermittently. The analyzed data can be asubset of the data collected or the analyzed data can be all of the datacollected. For example, the analyzed data can be intermittent samplesredacted from the results of continuous hydration monitoring.

One advantage of the analysis of hydration monitoring results obtainedover extended periods of time is that long term monitoring may beachieved. The monitoring can be long term in that diurnal, monthly, orother variations in hydration that are not associated with diseasestates can identified. The monitoring can be individualized in that theanalysis results are relevant to a specific monitored organism.

Data analysis can accommodate both long and short term variations inhydration that are not associated with disease states by reducing theeffect of such variation on analysis. For example, data analysis canaccommodate variations associated with respiration and other types ofmovement. For example, peak/trough analysis and/or frequency analysis ofhydration monitoring results obtained from the chest can be used todetermine the breathing period. This can be done, e.g., by identifyingthe rate of change between discrete data points in the measurementresults. Once the breathing period is identified, specific measurementresults (such as those associated with exhalation) can be identified andrelied upon in subsequent analyses.

Changes in impedance measurements due to electrode movement over time orwith wear can also be accommodated in data processing routines ifnecessary.

As another example, data analysis can accommodate diurnal or monthlyvariations. Such variations can be identified by peak/trough analysisand/or frequency analysis of longer term measurement results. Forexample, specific measurement results (such as those associated withexhalation) can be used to identify any reproducible diurnal and/ormonthly variability in hydration. Such variability can be accommodatedin subsequent measurement results by subtraction of the priorvariability or other adjustment approaches.

For example, the diurnal pattern of hydration monitoring results mayindicate that there is a significant likelihood of a 3% decrease in abioelectric impedance value for a specific organism in the lateafternoon relative to early morning. Hydration measurement resultsobtained at either time may be adjusted or modified by interpolation toreflect the decrease. Such adjustments can be made to account forpredictable or habitual patterns such as, e.g., daily exercise routinesor eating/drinking habits.

As another example of accommodating diurnal variations, only measurementresults obtained during patterned times of regular breathing (forexample, during sleep) are relied upon in subsequent analyses. Suchpatterned times can be identified, for example, by determining the rateof change in hydration monitoring results. Such patterned times can beused in conjunction with measurement results obtained with a knownhydration status (e.g., the monitored individual is “dry” and unaffectedby pulmonary edema) to adjust decision criteria and other analysisparameters.

Other variations in hydration monitoring results, including randomvariations such as electronic stray signal or positional signal noise,can be accommodated using digital and/or analog filters, signalaveraging, data discarding techniques, and other approaches.

Data analysis of hydration monitoring results can be used to establish abaseline of typical hydration characteristics so that deviations fromthe baseline, e.g., in response to disease states or other stresses, canbe identified. The baseline of typical hydration characteristics can beindividualized and relevant to a specific monitored organism, or thebaseline of typical hydration can reflect the average hydration of apopulation of individuals. For example, extended monitoring results canbe analyzed to establish a population database of tolerances and rangesfor the identification of individual disease states, deviations, and/oranomalies, as well as population trends (as discussed further below).Such a baseline can be obtained for healthy and/or diseased populationswith a variety of demographic characteristics.

In contrast, transient periodic hydration monitoring of an individual(such as, e.g., monitoring an individual for a short time once a day oronce a week) is less likely to detect individual variations, deviations,or anomalies and does not contribute to the establishment of apopulation database.

Data analysis can include the analysis of subsets of the total hydrationmonitoring results. The analyzed subsets can have common characteristicsthat distinguish the subsets from unanalyzed hydration monitoringresults. For example, the analyzed subsets can have high signal-to-noiseratios, analyzed subsets can be obtained under dry conditions (e.g.,when surface impedances 1515, 1520, 1525 (FIG. 15) are relatively high),analyzed subsets can be obtained when good contact is maintained betweena monitored organism and inputs 120, 125 and outputs 130, 135 (FIG. 1),or analyzed subsets can be obtained at the same time of day.

Data analysis operations can be performed at one or more of probe 100,data collection apparatus 1105, and/or data management system 1110. Inone implementation, data analysis is distributed between probe 100 anddata collection apparatus 1105. In particular, probe 100 can performinitial analyses, including signal processing, noise filtering, and dataaveraging operations. The operations can be performed on data from oneor more measurements taken at one or more frequencies. The operationscan be performed on raw data or on data where variations have beenaccommodated. For example, the operations can be performed on datacollected at certain points during breathing. These initial analysisresults can be transmitted, along with other information such as a probeidentifier and a time/date stamp, to data collection apparatus 1105. Atdata collection apparatus 1105, data analysis operations can include theidentification of trends or shifts in hydration associated with diseasestates such as pulmonary edema, as well as comparisons between receiveddata and threshold values.

In another implementation, data analysis operations are performedprimarily at data collection apparatus 1105 and data analysis at probe100 is minimal. When data analysis at probe 100 is minimal, dataanalysis and data storage can be consolidated at data collectionapparatus 1105 and probe 100 can include simplified circuitry withreduced power requirements and cost.

Data analysis can also be performed at data management system 1110. Suchdata analysis can include multivariable analysis where hydrationmonitoring results are analyzed in light of other statistical variablessuch as weight, heart rate, respiration, time of day, month, eatingpatterns, physical activity levels, and other variables. The otherstatistical variables need not be entirely independent of the hydrationmonitoring results. The hydration monitoring results used inmultivariable analysis can be obtained over extended periods (e.g.,days, weeks, or months) from one or more organisms. The results of suchmultivariable analysis can be used to develop new and improved analysesof hydration monitoring results, including improved algorithms, improvedpattern definition techniques, and/or artificial intelligence systems.

A variety of other analysis techniques can be applied to hydrationmonitoring results. These include the use of established guidelinevalues for data that is used to determine fluid changes associated withthe onset or progression of pulmonary edema. Also, clinician-modifiedvariables such as tailored threshold values can be applied to permitincreased accuracy and specificity.

These and other analyses of hydration monitoring results can be made inlight the results of monitoring other biological parameters such asrespiration, heart rate, hormone (e.g., B-type natriuretic peptide(BNP)) levels, metabolite levels (e.g., blood urea nitrogen (BUN) and/orNa⁺/K⁺ levels), wedge pressure measurements, electrocardiogrammeasurements, and others. Analyses made in light of such otherparameters may improve the information provided by the analysis process.

Data analysis can include comparisons involving recent hydrationmonitoring results. For example, recent hydration monitoring results canbe compared with previous hydration monitoring results, predictedresults, or population results. Future hydration monitoring results canbe predicted based on the current state of the monitored individual andon past hydration monitoring results obtained with the same or withother individuals or a population or demographic group. Such comparisonsmay include, for example, the use of population data tables, multiplereference measurements taken over time, or the results of trend analysesbased upon extended hydration monitoring.

Such comparisons can also involve other factors, including otherbioparameters. For example, hydration monitoring results can be weightedby one or more factors before comparisons are performed. Examples ofsuch factors include the monitored individual's age, weight, height,gender, general fitness level, ethnicity, heart rate, respiration rate,urine specific gravity value, blood osmolality measurement, time of day,altitude, state of hydration (either subjective or objective), cardiacwaveforms, left ventricle ejection fraction, blood oxygen levels,secreted potassium or sodium ions levels, skin surface temperature,ambient temperature, core body temperature, activity/motion assessment,humidity, and other bioparameters.

With trend analysis and prediction of future hydration state, it ispossible to prevent serious hydration related problems, e.g. severeblood loss, from occurring by providing treatment or interventionrecommendations to the subject and/or a care provider prior to serioushydration problems occurring. For most subjects, a rapid downwardhydration trend, e.g. blood loss from external injury, over a selectedperiod, e.g. 1 hour, could be detected automatically and presented tothe subject and/or remote monitor. The timing and nature of thedetection could be also based at least in part on the age, gender, orother relevant factors. For some conditions, a recommended intake of apharmaceutical agent can be automatically provided.

Hydration monitoring can proceed in a variety of different environmentsusing a variety of different procedures to monitor a variety ofdifferent conditions. For example, in one implementation, wherehydration is monitored for indications of pulmonary edema, monitoringcan commence after an individual has been identified as at risk forpulmonary edema. For example, such an individual may have been admittedto a care facility for treatment of pulmonary edema. Hydration can bemonitored as the individual is “dried out” and excess fluid load in thethoracic region is reduced. Hydration monitoring can be continued afterthe individual is “dried out” to avoid excessive fluid loss.

Hydration monitoring can be performed to achieve a variety of differentobjectives, including the identification of levels and distributions ofwater in organisms that are indicative of one or more acute or chronicconditions or disease states. Examples of such monitoring follow.

Many individuals find themselves in activities or in environments thatare conducive to dehydration. Such activities may include athletics,public safety activities performed by officers/firefighters, combat, andother activities requiring physical exertion. Such activities are oftenperformed in environments that are hot and humid.

In these cases, one or more strap probes can be deployed along a thighof such individuals to continually monitor the hydration of suchindividuals. Alternatively, probes can be incorporated into clothingsuch as the pants and sock illustrated in FIGS. 9A and 9B.

During the initialization of hydration monitoring, a range of data,including hydration monitoring results and the results of monitoringother bioparameters, can be transmitted to one or more data processingdevices that perform analysis operations. The transmitted data can beused by such devices to establish a baseline from which relative changesin hydration can be determined. The transmitted data can include, e.g.,urine specific gravity, blood osmolality, and/or other parametersindicative of hydration status, including, e.g., anthropometric datasuch as segment size, age, height, weight, and general fitness level.

The established baseline can be returned to the probe and used by theprobe to provide instantaneous alarms when hydration monitoring resultsindicative of dehydration are obtained. Further, the results ofhydration monitoring generated by the probe can be transmitted to a datacollection apparatus and/or data management system for analysis andarchiving.

A data collection apparatus and/or data management system can alsoidentify hydration monitoring results that are indicative ofdehydration. For example, when hydration decreases by a certainthreshold amount (e.g., 3%), a data collection apparatus and/or datamanagement system can record the decrease and then trigger an alarmsignal at the probe and/or the data collection apparatus. For example,the extent of dehydration can be displayed along with a recommendedfluid replacement volume and a recommended recovery time. Further, thealert can be relayed to a third party such as an athlete's coach, asupervisor, or medical personnel.

Following a period of monitoring, the monitored individual can removeand replace a probe. The new probe can synched to the data collectionapparatus and provided with new baseline impedance measurements.

1. Hydration Monitoring of Military Personnel

The systems and methods described herein may be used for monitoring ofsoldiers. A soldier wearing the hydration monitoring patch who isdeployed on a mission could be periodically notified of his/herhydration status. The notification could indicate that if he/shecontinues at the current dehydration rate he/she will begin to losecritical performance capabilities within a certain amount of time. Basedupon this information, the soldier could respond prior to losing thiscapacity by actively replenishing fluids until an “OK” status notice isdisplayed.

2. Bioelectric Impedance Monitoring of Individuals Using a DataCollection Apparatus Incorporated into Other Equipment

A data collection apparatus can be incorporated into a device commonlyused by individuals who find themselves in activities or in environmentsthat are conducive to dehydration. For example, a data collectionapparatus can be incorporated into safety equipment, the handlebars of abicycle, a helmet, or gloves. When hydration monitoring resultsindicative of a disease state such as dehydration are obtained, the datacollection apparatus can alert the individual and/or others in theindividual's vicinity of the results. For example, a light on theoutside of a football player's helmet can flash to alert teammates andcoaches of the player's hydration monitoring results. These alerts canbe graded with the severity of the hydration monitoring results so thatthe player and teammates have timely warning prior to passing criticalhydration thresholds, such as greater than 5% dehydration.

3. Bioelectric Impedance Monitoring of Individuals in Motorized Vehicles

Many individuals who operate motor vehicles are ambulatory but havetheir mobility restricted in that they are confined within the vehiclefor extended times. Such vehicles include cars, airplanes, tanks, ships,and other transportation devices.

Probes for monitoring the hydration of such individuals can beincorporated into motor vehicles, e.g., at a steering wheel, joystick,or other surface that contacts operating individuals either continuallyor intermittently. Intermittent contact can be accommodated by limitingdata analysis to data obtained during periods of good contact betweenthe probe and the monitored organism.

Such vehicles can also include a data collection apparatus. In someimplementations, the data collection apparatus can share genericcomponents with the vehicle to perform various operations. Suchcomponents include vehicle display systems and data communicationdevices.

When hydration monitoring results indicative of a disease state such asdehydration are obtained, the data collection apparatus can alert theindividual and/or others in the individual's vicinity of the results.For example, a pit crew can be notified that a driver is becomingdehydrated or a commanding officer can be notified that soldiers inhis/her command are becoming dehydrated.

4. Bioelectric Impedance Monitoring to Monitor Acute Blood Loss,Systemic Hemorrhage or Hypervolemia of a Subject

As mentioned above, many individuals find themselves in activities or inenvironments that pose a serious risk of injury such as the loss ofblood. Such activities may include athletics, public safety activitiesperformed by officers/firefighters, combat, and other activitiesrequiring physical exertion.

Individuals may suffer acute blood loss through external bleeding orsystemic hemorrhage/internal bleeding. Sometimes a first respondercaring for such an individual may overhydrate an injured individual,which can result in hyperhydration or a state characterized by anabnormal increase in the volume of blood (hypervolemia).

In these cases where there is a serious risk of injury, such asfirefighting, disaster response, combat, or police work, one or morepatch or strap probes as described above can be deployed along a thigh,chest or to another portion of such individuals to monitor the hydrationstate of such individuals.

For example, external blood loss depletes body water at a rate beyondtypical for dehydration. Internal bleeding causes either blood to poolin certain areas or it reduces vascular blood volume at the injury site,or both. In some embodiments two or more probe electrodes are connectedto the subject near a location of suspected internal bleeding. Thesystem may detect the change in tissue impedance caused by the bloodpooling and/or reduced vascular blood volume at the injury site, therebyidentifying the disease state.

The systems and methods described herein would be of great benefit formany individuals. For example, a soldier or firefighter wearing animpedance monitoring patch might be wounded in a remote area. The woundcould be either external or internal blood loss. The system could alertboth the soldier/firefighter and command structure of the severity ofthe blood loss, enabling an appropriate medical response to theinjury/wound. To alert the soldier and the command structure the systemmay vibrate, send a wireless signal, or display an image or a message ona display. Other alerts may also be performed.

In some embodiments, the impedance data is wirelessly communicated to aremote device. The remote device may analyze the data, and maywirelessly communicate a result of the analysis to the probe. In someembodiments, the probe may alert the soldier or firefighter of theresults of the remote analysis.

As another example, the system could be used to measure hydration of asubject by, for example, first responders at accident scenes, ambulancepersonnel, and the like. Occasionally medics do not properly diagnoseinternal bleeding, and in the case of external bleeding, sometimesrespond too aggressively to injuries by delivering too much body fluidreplacement, resulting in either euhydration, hyperhydration orhypervolemia. This places increased strain upon the injured individual'sheart and other vital organs. Use of the present system and methoddetects internal bleeding, and also detects euhydration, hyperhydrationand hypervolemia and alerts the medic so that proper measures may betaken during transit or upon arrival at the more advanced treatmentlocation. It will be appreciated that in this embodiment, a hand-heldprobe or individual electrodes may be used by the attending medicalpersonnel instead of a patch or strap.

In some embodiments, a probe may sense other biometric data, such astemperature, dermal heat flux, vasodilation and/or blood pressure. Thisdata may be analyzed along with impedance data to further characterizethe condition of the subject. Hyperhydration and hypervolemia may resultin vasodilation and the system monitoring both the bioelectric impedancespectroscopy and vasodilation could identify these disease states.

Although a number of implementations have been described, changes may bemade within the spirit and scope of the present invention. Accordingly,other implementations and embodiments are within the scope of thefollowing claims.

1. A method of detecting and/or monitoring hypovolemia, hemorrhage orblood loss of a subject, said method comprising making impedancemeasurements of at least a portion of said subject while said subject isinjured.
 2. The method of claim 1, comprising connecting two or moreelectrodes to said subject.
 3. The method of claim 2, wherein connectingthe two or more electrodes comprises connecting a patch or strap probeto the subject.
 4. The method of claim 2, wherein connecting the two ormore electrodes to the subject comprises wearing an article of clothingto which said electrodes are attached.
 5. The method of claim 1, furthercomprising: making said impedance measurements at two or more points intime; and determining whether the subject is externally bleeding basedon a change in measured impedance.
 6. The method of claim 1, furthercomprising: making said impedance measurements at two or more points intime; and determining whether the subject is internally bleeding basedon a change in measured impedance.
 7. The method of claim 6,additionally comprising diagnosing an internal bleeding condition basedon said change in measured impedance.
 8. The method of claim 1,additionally comprising infusing said subject with fluid so as torehydrate said subject until said impedance measurements reach apredetermined state.
 9. The method of claim 1, further comprisingproviding an indication of the blood loss condition to at least one ofthe subject, medical personnel, and a remote location.
 10. The method ofclaim 1, further comprising wirelessly communicating the blood losscondition to a remote apparatus.
 11. The method of claim 1, furthercomprising remotely analyzing the data.
 12. The method of claim 1,further comprising sensing at least one of temperature, vasodilation andblood pressure.
 13. A method of monitoring a hydration condition of aninjured subject, comprising: monitoring a bioelectric impedance of atleast a region of the injured subject; generating data related to thehydration condition of the subject; and communicating the hydrationcondition to medical personnel attending the subject.
 14. The method ofclaim 13, further comprising determining whether the subject is at leastone of dehydrated, hyperhydrated, and hypervolemic.
 15. The method ofclaim 13, further comprising wirelessly communicating at least one ofthe data and the hydration condition to a remote apparatus.
 16. Themethod of claim 15, further comprising remotely analyzing the data. 17.The method of claim 13, further comprising sensing at least one oftemperature, heat flux, vasodilation and blood pressure.